1. Field of the Invention
The present invention relates to a process for producing a synthetic coking coal which is used as a source of coal for producing a blast furnace coke by coking heavy hydrocarbons such as atmospheric residual oil or vacuum residual oil under the coking conditions of reduced partial pressure or reduced total pressure. More particularly, the present invention relates to a process for producing a low sulfur fuel oil by hydrodesulfurization of the thermally cracked oil which is formed in the coking reaction in high yield.
2. Description of the Prior Art
Recently, difficulties have been encountered in obtaining adequate supplies of coal for producing blast furnace coke because of the shortage of coal. Thus, alternative sources of coke such as the coke produced by coking a petroleum residual oil fraction has been used as the source of a portion of the coal required for producing metallurgical coke in many blast furnaces applications. However, the conventional coke produced by coking a petroleum residual oil fraction (delayed coking, fluid coking, etc.) has inferior coking properties and low fluidity. These factors have limited the amounts of this type of coke which have been blended with other cokes. Accordingly, this type of coke has only been used as a low ash content carbon source.
The thermally cracked oil obtained by the coking of residual oils contains a substantial low boiling fraction and only a small amount of a high boiling fraction.
Another factor which has influenced the use of residual oils is the increased amount of pollution caused by the sulfur dioxide liberated by the increased consumption or combustion of heavy fuel oil. Thus, it has been necessary to thoroughly treat vacuum residual oils having high sulfur contents which are produced as a by-product in refinery operations.
A need, therefore, exists for a synthetic coking coal having good coking properties and fluidity which is used as a raw material for blast furnace coke and which is produced from a thermally cracked residual oil. The cracked oil is produced in high yield, and is hydrodesulfurized to produce a low sulfur fuel oil.